The broad objective of the research is to correlate structure and function in biological membranes. Of special interest are the roles of phospholipase in membrane modification in response to changes in environment. Phospholipases are present in all biological membranes but their physiological function remains unknown. Since many, if not most, membrane components are allotopic (depend upon hydrophobic environment for activity), it is likely that alteration of the membrane phospholipids will perturb function of the various neighboring membrane components. Thus it is likely that phospholipase A activation, resulting in deacylation of membrane lipids and thereby creating an alteration in the hydrophobic environment about membrane enzymes, will result in a change in activity. Phospholipases may be activated by a variety of changes including T4 phage ghost attachment, heat, colicins, solvents, and EDTA. Functional changes which occur concurrently include lysis of cells, loss of lysis inhibition in phage infected cells, the inhibition of macromolecular synthesis, and loss of the non-specific permeability function of the outer membrane. This research seeks to determine the relationship between phospholipase activation and these changes in membrane function which occur simultaneously. Special emphasis is placed on the use of membrane perturbants, such as T4 phage and T4 ghost attachment, or EDTA, which activate phospholipase A under physiological conditions.